This invention generally relates to the use of chlorous acid for the production of chlorine dioxide in concentrations suitable for use as an oxidizing agent in various industrial processes, more particularly, for bleaching pulp in the paper industry. Other exemplary industrial processes where chlorine dioxide may be used as an oxidizing agent include disinfection in water and wastewater treatment systems to destroy pathogens, as a whitening agent in the paper industry and as a water treatment chemical in the oil recovery industry.
Methods and/or apparatuses for preparing chlorine dioxide have been described in the prior art. Ratigan, in U.S. Pat. No. 4,250,144, described a generating system for chlorine dioxide for use in the water or wastewater treatment industry. Ward et., al in U.S. Pat. No. 4,013,761, described an invention for generating chlorine dioxide including a generation vessel having leak inhibiting solvent weld joints with reducing couplings. Hartshorn, in U.S. Pat. No. 4,104,190, described a system of generating chlorine dioxide from aqueous liquids containing alkali metal or alkaline earth metal chlorites, and compounds which liberate chlorine in water. Rapson et al., in U.S. Pat. No. 4,534,952, described a small scaled generator of chlorine dioxide for water treatment. Rosenblatt et al., in U.S. Pat. No. 4,504,442, described a use of chlorine dioxide gas as a chemosterilizing agent particularly involving gas impermeable surfaces of implements commonly employed in the medical sciences. Callerame, in U.S. Pat. No. 3,754,079, described a process of preparing chlorine dioxide for use in the bleaching of wood pulp, fats, oils and flour. Capuano et al., in U.S. Pat. No. 4,542,008, described an electochemical process for producing chlorine dioxide from an aqueous solution of sodium chlorite. Hicks, in U.S. Pat. No. 4,590,057, described a process for the generation of chlorine dioxide from an aqueous solution of a metal chlorite and an oxidizing agent, preferably gaseous chlorine.
However, none of the prior art cited above discloses the unique method of preparing chlorine dioxide from chlorous acid for use for pulp bleaching as disclosed in the present invention.